This invention relates to a drive for a web fed rotary-roller offset printing machine with nine-roll or ten-roll printing mechanisms for optional impression-blanket or offset-offset operation and arbitrary reversibility of the individual inking rolls and plate/impression roll pairs.
Printing units of this kind are known from German Patent Specification No. 23 37 259 and U.S. Pat. No. 3,329,086. In order to make possible the establishment of driving connections for the various paper-guide and pressure modes, up to six special couplings must be actuated and up to four counter-shaft gear wheels must be brought into or out of engagement.
This type of drive construction involves a considerable gearing expenditure. In addition, the gear wheels located on a side wall of the main frame of the machine have a detrimental effect on the noise level on the operator's side of the machine.
Depending on the printing program, the drive is effected either from the plate roll to the blanket roll or inversely. Owing to the fact that the drive may be selectively in either direction, an adaptation of the diameter ratio of the rolls to the driving sequence for purposes of disturbance-free run-off is not possible. The fact that the roll pairs are freely adjustable relative to each other makes it necessary that the position of each roll pair must be individually detected if the switching or change-over operations are to be automated.
In prior printing units of this type, blanket rolls or cylinders are mounted in such a way that they can be applied either against the impression cylinder or else mutually in pairs against each other. By this long-known possibility of adjustment, one moving paper web can be printed in different variations, i.e. for instance, both sides in two colors, one side in one color and the other side in three colors or one side in four colors. Similarly, it is possible to print two paper webs in various combinations. The direction of rotation of each cylinder must be reversible.
The subject of the present invention is the drive of the cylinders for a printing unit of the type described above.
Drives in which the drive sequence changes depending on the cylinder position and the direction of rotation are known. The drive can be from the plate cylinder to the blanket cylinder and from there to the next blanket cylinder and the next plate cylinder. Also, the drive sequence for the first pair of cylinders can be reversed.